The present invention relates to a regenerative pump with a casing having a casing inlet and a casing outlet, wherein the radial forces generally acting on the impeller shaft in regenerative pumps are compensated so that the pump is suited for the generation of high, maximum pressures.
For attaining high pressures in case of relatively small conveying streams, multistage regenerative pumps are, as is known, particularly well suitable. Multistage regenerative pumps can be made of an especially simple structure by using only one impeller with an arrangement of several, different-diameter bucket rings with relatively short blades respectively on both sides of the impeller. Customarily, the buckets arranged on the outer periphery are separated from one another by a central web in the axial direction and operate in a side channel common to all of them. Since the pressure in the conveying medium increases steadily from the inlet of the side channel to its outlet, in the direction of travel, a resultant force component in the radial direction is produced by the pressure acting on the impeller. This radial force assumes considerable dimensions at high conveying pressures. In high-pressure pumps of this type, it is consequently necessary to provide reinforced shafts and likewise reinforced bearings. This involves considerable added expense, especially for the shaft seals, and also leads to an undesirably large diameter of the first conveying ring on the inside of the impeller.
DOS No. 2,105,121 discloses a regenerative pump wherein pressure pockets are arranged in the casing for compensating for these radial forces, the pressure pockets being in communication, through conduits, with the intake and delivery sides of the pump. The pressure pockets and the connecting conduits are arranged herein in such a way that the pressure ambient in the pressure pockets acts on a special part of the impeller provided for this purpose, so that the forces acting radially inwardly on the impeller by the pumping process are compensated. However, this solution requires additional control elements in the connecting conduits to obtain a corresponding adaptation of the pressure conditions built up in the pressure pockets to the respective conveying level and/or conveying pressure of the pump. Moreover, this arrangement must tolerate short-circuiting of the pump, leading to a flow of conveying medium from the delivery side via the throttling slots of the pressure pockets to the intake side, resulting in leakage losses. These losses considerably reduce the hydraulic degree of efficiency of the pump, particularly in case of small volume streams.
DOS No. 3,128,374 describes a regenerative pump, the impeller of which exhibits on both sides respectively one bucket ring with closed buckets, mutually separated side channels being arranged in opposition to these bucket rings, each of these side channels exhibiting an entrance port and exit port, as well as an interrupter. The conveying medium flows in this pump in two mutually separated conveying streams via the side channels from the respective side channel entrance to the respective side channel exit. However, the radial forces mentioned above also occur in this pump.
Starting with the above-discussed state of the art, it is an object of the present invention to provide an improved regenerative pump so that the shaft of the impeller essentially needs to transmit and/or absorb only torques.
This object is achieved by providing that the entrance ports are connected with the casing inlet and the exit ports are connected with the casing outlet for the subdivision and subsequent recombination of the conveying streams. Also the entrance port, the exit port, and the interrupter are arranged with respect to the first impeller side in the direction of rotation of the impeller to be offset by such an angular amount with regard to the corresponding elements on the second side of the impeller that the radial forces on the first impeller side, resulting from the pressure differences in the conveying streams between the inlets and the outlets, are opposed by radial forces on the second impeller side that are equal in amount, but act in the opposite direction.
By this procedure, which can be structurally realized very easily, the radial forces that perforce occur are already compensated for in the impeller so that there are no longer any radial forces effective on the shaft of the impeller. It is thereby possible, on the one hand, to make the shaft bearing, with the associated seal, economically of a smaller size, without reducing the lifetime of the pump. moreover, due to the smaller dimensioning of the impeller shaft, an internal blade ring can be provided which has a small diameter and a correspondingly low peripheral speed during operation. Due to the fact that the peripheral speed is low, the acceleration impact on the conveying medium while entering the pump, which lowers the degree of efficiency, is reduced.
It is furthermore possible by the arrangement of the present invention to mount a plurality of blade rings of varying diameters with corresponding side channels, i.e. a plurality of series-connected pumping elements, on a single impeller. This has not been possible on account of the heretofore occurring radial forces and has been circumvented by distributing the pressure stages over several, respectively separately supported impellers.
The solution of the present invention provides a still further advantage in multistage impellers by the feature that the individual blade rings can be respectively constructed with axially and radially open bucket compartments wherein sealing between the conveying stages is effected by radial sealing gaps so that the bucket rings can be staggered in the theoretical minimum spacings. By such minimum spacing, in turn, the above-mentioned acceleration impact on the conveying medium when passing from one stage into the subsequent stage, with its deleterious effects, is diminished. This feature also could not be exploited heretofore since this mode of construction results in very broad impellers leading to undesirably large bearing spacings.
Therefore, in the present regenerative pump, the two impeller and side channel sides, sealingly separated from each other, act inversely, i.e. the respective pressure buildup along the side channel periphery of one side takes place offset by 180.degree. about the shaft axis, i.e. in opposition to the other side channel side. Accordingly, equal-size radial forces oppose each other at any point of the side channel periphery so that the radial forces produced on both sides of the impeller are automatically equalized essentially without losses and without auxiliary devices, in every operating point of the pump.
Due to the structure of the pump, which is free of radial forces, the otherwise occurring vibrations of the shaft due to its bending are likewise avoided so that the lifetime of the pump is thereby further increased.
The tilting moment produced by the axial forces opposed on the two impeller sides extends in opposition to the tilting moment acting on the two impeller sides by the radial forces. Thus, with a corresponding dimensioning of the depth of the impeller, a compensation of moments and accordingly an essentially force-free shaft (except for the torques) can be attained.